Transcript Chapter3RHS13Part2x

Ecosystems: What Are They
and How Do They Work?
Chapter 3, Part 2
Key Concepts
•
• PART 1:
Ecology: Earth and ecosystems
Energy flows
• PART 2:
Matter cycles
Studying ecosystems and human impacts
PART
2
Section 3-4
WHAT HAPPENS TO MATTER IN AN
ECOSYSTEM?
Nutrients cycle within and
among ecosystems: CHNOPS
• Elements and compounds move through air, water,
soil, rock and living organisms in biogeochemical, or
nutrient, cycles.
• Major nutrients cycling through the biosphere:
• Carbon (carbon cycle)
• Hydrogen (water/hydrologic cycle)
• Nitrogen (nitrogen cycle)
• Oxygen (through photosynth. and cellular respiration)
• Phosphorous (phosphorous cycle)
• Sulphur (sulphur cycle)
The Water/Hydrologic Cycle
Solar energy evaporates
water; the water returns
as precipitation (rain or
snow), goes through
organisms, goes into
bodies of water, and
evaporates again.
Water is filtered and
partly purified as it
moves through the
hydrological cycle.
Water can be stored as
ice in glaciers or in
underground aquifers.
Water is unique. It…
• Is held together by hydrogen
bonds.
• Exists as a liquid over a wide
temperate range.
• Stores a large amount of heat.
• Requires a large amount of
energy to be evaporated.
• Dissolves a variety of
compounds.
• Filter’s some UV rays from the
sun.
• Can move through capillary
action.
• Expands when freezes.
• Exists in all three phases at the
Earth’s surface.
Human Impacts on the water
cycle
• Humans alter the water cycle in many
ways:
• Withdrawing freshwater at faster rates than
nature can replenish it.
• Clearing vegetation which increases runoff
and decreases replenishment of groundwater
supplies.
• Draining wetlands which interferes with flood
control.
• Pollution addition of nutrients and/or toxins
The Carbon Cycle
Carbon is the
basic building
block of
carbohydrates,
fats, proteins,
DNA, and other
compounds.
Carbon circulates
through the
biosphere (all
living things),
hydrosphere, and
atmosphere.
Carbon Cycle Animation
Carbon cycle animation- LEARN THE CARBON CYCLE!
http://www.cengage.com/earthscience/book_content/9781111988937_miller/animat
IMPORTANT: Cellular respiration and other chemical break-down of
matter (ie burning), photosynthesis, atmosphere, ocean, biosphere
Human Impacts on the Global
Carbon Cycle
High
projection
1. Clearing Vegetation
Low
projection
2. Burning Fossil Fuels
Consider the
consequences…
Fig. 3-26, p. 56
The Nitrogen Cycle
Nitrogen gas (N2)
makes up 78% of
the atmosphere
BUT N2 cannot
be used directly
by most living
organisms.
Nitrogen-fixing
bacteria convert
N2 into
compounds that
are useful
nutrients for
plants and
animals.
The Nitrogen Cycle
Synthetic Nitrogen
Fixation
by industry
for agriculture
(leads to nitric oxide
NO,nitrous oxide N2O,
nitrogen dioxide NO2pollution)
Fertilizers
uptake by
autotrophs
Gaseous Nitrogen (N2)
in Atmosphere
Food Webs
on Land
excretion, death,
decomposition
uptake by
autotrophs
Nitrogenous Wastes,
Remains in Soil
NO3–
in Soil
Nitrogen Fixation
bacteria convert N2 to
ammonia (NH3); this
dissolves to form
ammonium (NH4+)
NH3, NH4+
in Soil
loss by
leaching
Denitrificatio
n
by bacteria
Ammonification
bacteria, fungi convert the
residues to NH3; this
dissolves to form NH4+
1. Nitrification
bacteria convert NH4+
to nitrite (NO2–)
2. Nitrification
bacteria convert NO2–
to nitrate (NO3–)
NO2–
in Soil
loss by
leaching
N Cycle Animation
Nitrogen cycle interaction - LEARN THE NITROGEN CYCLE!
Nitrogen fixation, Ammonification, Nitrification, Denitrification
N is a common limiting factor in agricultural systems
(More animations on textbook website)
http://www.cengage.com/earthscience
/book_content/9781111988937_miller/
animations/ch03/animation_media/nitr
ogen_cycle_v2/nitrogen_cycle_v2.htm
l
Human Impacts on the N Cycle
Human agricultural practices have more than doubled the
amount of N in the atmosphere and hydrosphere.
1. Production of inorganic fertilizers and the
burning of fossils fuels produce:
• Nitrogen oxides (NOx) cause smog and
acid rain (includes nitric oxide NO, nitrogen dioxide NO2),
AND
• Nitrous oxide (N2O), a powerful
greenhouse gas
2. Excess Nitrate (NO3-) from fertilizer,
agricultural waste, and sewage can leach thru
soil to contaminate groundwater and
become runoff that causes eutrophication
The Phosphorus Cycle
Phosphorus
circulates
through
water, rock,
and living
things.
Phosphorus
does not
cycle
through the
atmosphere.
Major
reservoirs:
rock, ocean
bottom.
P Cycle Animation
Phosphorus cycle animation
P is the most common limiting nutrient in
natural ecosystems
http://www.cengage.com/earthscien
ce/book_content/9781111988937_m
iller/animations/ch03/animation_med
ia/phos_anim/phos_anim.html
Human Interventions in the
Phosphorus Cycle
1. Mining of phosphate rock
2. Clearing tropical forests reduces available
phosphate in tropical soils
3. Phosphates from runoff of animal wastes, sewage
& fertilizers disrupts aquatic ecosystems
- eutrophicationSince 1900, human activities
have increased the natural rate of phosphorous
release to environment by about 3.7 fold.
The Sulfur Cycle
Much of the
earth’s sulfur is
stored
underground in
rocks and
minerals.
Hydrogen
sulfide (H2S) is
released from
volcanoes and
anaerobic
decomposition
of organic
matter in bogs
and swamps.
Sulphur Cycle Animation
http://www.cenga
ge.com/earthscie
nce/book_content
/9781111988937_
miller/animations/
ch03/animation_
media/sulfur_cycl
e/sulfur_cycle.htm
l
S in the atmosphere can lead to acid rain and smog
Sulfur cycle animation
Humans have been increasing atmospheric sulfur dioxide (SO2)-which causes acid rain and smog--by burning sulfur-containing
fuels, refining sulfur-containing fuels, and converting sulfur
containing metallic mineral ores into free metals.
•
Nutrient cycling in the environment
impacts life in the environment
• Limiting factor principle- Too much or too little of any abiotic
factor can limit or prevent growth of population.
• Limiting factors:Excess water or water shortages for
terrestrial organisms
• Excess or lack of soil nutrients
Dissolved oxygen for aquatic organisms
Salinity for aquatic organisms
Pollution
Range of Tolerance
Upper limit
of tolerance
Lower limit
of tolerance
Few
organisms
Abundance of
organisms
Few
organisms
No
organisms
Population Size
No
organisms
Zone of
intolerance
Low
Zone of
physiological stress
Optimum range
Temperature
Zone of
Zone of
intolerance
physiological stress
High
Nutrient and Pollution Levels Influence
Populations
•
• Range
of tolerance:
range of abiotic conditions required for population to survive
• Law of tolerance
“The existence, abundance and
distribution of a species in an ecosystem are determined by
whether the levels of one or more physical or chemical factors
fall within the range tolerated by that species.”
Section 3-5
HOW DO SCIENTISTS STUDY
ECOSYSTEMS?
How Do Ecologists Learn about
Ecosystems?
• Field research.
Gather comparative baseline data.
• Remote sensing
• Geographic information system (GIS). Example:
computerized maps of an area that are used to examine forest cover, water
resources, air pollution emissions, coastal changes, and changes in global
sea temperatures.
• Laboratory research
• Systems analysis, Mathematical models, Simulations.
All rely on accurate input of “real world” parameters.
Three Big Ideas
• PART 1: Life is sustained by the flow of energy
from the sun through the biosphere, the cycling
of nutrients within the biosphere, and gravity.
• PART 2: Some organisms produce the
nutrients they need, some survive by
consuming other organisms, and others recycle
nutrients back to producers.
• Human activities are altering the flow of
energy through food chains and webs, and the
cycling of nutrients within ecosystems and the
biosphere.